This invention is generally directed to toner and developer compositions. More specifically, the present invention relates to toner compositions containing a highly crosslinked styrene resin. In one embodiment, thus there are provided in accordance with the present invention toner compositions comprised of highly crosslinked styrene methacrylate, or styrene acrylate resin particles, pigment particles, low molecular weight wax components, first additive particles, and second additive particles. Also, in another embodiment of the present invention developer compositions are formulated by admixing the aforementioned toners with carrier particles, preferably uncoated ferrites. The toner and developer compositions of the present invention are particularly useful in electrophotographic printing, and imaging methods, especially xerographic processes with soft roll fusers, and wherein release agents, such as silicone oils selected to prevent toner particles from adhering to the surface of fuser rolls, are avoided.
Toner compositions with crosslinked resins are known, for example, in U.S. Pat. No. Re. 31,072 (a reissue of 3,938,992), a toner composition with styrene crosslinked resin particles is disclosed, which resins are crosslinked to a sufficient extent to extend the useful fusing range by at least 10.degree. C. as compared to uncrosslinked toner resins. Developer compositions and modifying materials for the toner are also disclosed in the '992 patent, see column 14, beginning at line 47, for example. A similar disclosure is presented in U.S. Pat. No. 3,941,898, the disclosure of which is totally incorporated herein by reference. In addition, there are illustrated in U.S. Pat. No. 4,513,074, the disclosure of which is totally incorporated herein by reference, stable conductive developer compositions comprised of first resin particles of styrene methacrylate copolymers grafted with, or containing a low molecular wax composition; second resin particles of a styrene, acrylate, acrylonitrile terpolymer; pigment particles; colloidal silica additive particles; fatty acid metal salt additives; and uncoated ferrite particles. The developer compositions of the present invention are similar to those illustrated in the aforementioned patent with the primary exception that there is selected in place of the first resin, and second resin particles a crosslinked styrene resin as illustrated hereinafter, which enables the formation of a more economical toner, and also provides other advantages.
Further, there are described in U.S. Pat. No. 4,604,338 positively charged dry toner compositions with colored pigments excluding black, which compositions contain first resin particles, second crosslinked resin particles, a low molecular weight wax, and certain charge enhancing additives. Additionally, toner and developer compositions, especially those containing charge enhancing additives, are well known, reference for example, U.S. Pat. Nos. 3,893,935; 3,944,493; 4,007,293; 4,079,014 and 4,394,430. Further, there is disclosed in U.S. Pat. No. 4,338,390 developer and toner compositions having incorporated therein as charge enhancing additives organic sulfate and sulfonate substances. A similar disclosure is present in U.S. Pat. No. 4,394,430. Moreover, there are disclosed in U.S. Pat. No. 4,298,672 positively charged toner compositions with resin particles and pigment particles; and as a charge enhancing additive, alkyl pyridinium compounds, inclusive of cetyl pyridinium chloride.
Additionally, toner and developer compositions useful in xerographic imaging processes, wherein silicone oils are not needed, are known, reference for example U.S. Pat. No. 4,556,624, the disclosure of which is totally incorporated herein by reference. In this patent, there are disclosed improved positively charged toner compositions comprised of a polyblend mixture of crosslinked copolymer compositions, a second polymer, pigment particles, and a particular wax component thereby enabling the toner compositions to be selected for imaging systems wherein release fluids are not required. The types of resin described in this patent and other patents relating to toner compositions, including those compositions useful in imaging methods without the need for release agents are polyamides, epoxies, diolefins, polyurethanes, vinyl resins, and polymeric esterification products of a dicarboxylic acid and a diol comprising a diphenol. Specific examples of known vinyl resins include homopolymers or copolymers of two or more vinyl monomers. Typical vinyl monomers are styrene, p-chlorostyrene, unsaturated mono-olefins such as ethylene, propylene, butylene, isobutylene and the like; vinyl esters such as esters of monocarboxylic acids including methyl acrylate, ethyl acrylate, n-butylacrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methylalphachloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and other similar acrylates; acrylonitrile, methacrylonitrile, acrylimide; vinyl ethers, such as vinyl methyl ether, vinyl isobutyl ether, vinyl ethyl ether, and the like; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl keton; and N-vinyl indole, N-vinyl pyrrolidene, and the like; styrene butadiene copolymers; and mixtures thereof.
As preferred toner resins illustrated in the '624 patent, there can be selected styrene polymers and the esterification products of a dicarboxylic acid, and a diol comprising a diphenol. The aforementioned polyesters are illustrated in U.S. Pat. No. 3,590,000. Other specific preferred toner resins include styrene/methacrylate copolymers, styrene/butadiene copolymers, polyester resins obtained from the reaction of bisphenol A and propylene oxide, followed by the reaction of the resulting product with fumaric acid, branched polyester resins resulting from the reaction of dimethylterephthalate, 1,3-butanedil, 1,2-propanediol, and pentaerythritol; and styrene butadiene copolymers prepared by a suspension polymerization process, reference U.S. Pat. No. 4,558,108.
Furthermore, illustrated in U.S. Pat. No. 3,418,354 are processes for obtaining olefin-polyoxyalkylene copolymers by a graft reaction with a peroxide whereby there are generated free radical sites on the backbone polymer. One process embodiment disclosed in the '354 patent involves the addition of an alpha olefin such as styrene, and a peroxide to a polyoxyalkylene compound, such as a siloxane, wherein there results a graft copolymer; and more specifically, an olefin-polyoxyalkylene graft copolymer, see column 2, line 23. In Japanese Patent Publication No. 46-9355, there is disclosed a procss for the preparation of graft block copolymers with a polysiloxane chain by the reaction of a functional polysiloxane with a polymer obtained from the anion polymerization of a styrene or a butadiene. Japanese Patent Publication No. 58-225103 discloses a method for the crosslinking of a thermoplastic resin by the reaction of a hydrogenated styrene-butadiene-styrene block copolymer with a silane in the presence of organic peroxides. Further, in U.S. Pat. No. 3,691,257 there are disclosed organic polymers modified by incorporating therein a polymer siloxane organic block copolymer; while Japanese Patent Publication No. 57-187345 describes a rubber modified styrene resin prepared by continuous bulk polymerizations in the presence of organic polysiloxanes and 1,2-vinyl polymers.
Other representative patents primarily of background interest include U.S. Pat. No. 4,237,257 relating to methods for preparing low molecular weight styrene series polymers useful as toners, which preparation involves the selection of an organic peroxide initiator; U.S. Pat. No. 4,339,337 relating to a suspension polymerization method for the preparation of magnetic beads from vinyl aromatic polymers, including styrenes, and where benzoyl initiators may be selected, reference column 3, line 17. Additionally, this patent indicates that a crosslinking monomer, reference divinylbenezene, may be added, reference column 2, line 39; and U.S. Pat. No. 4,617,249 relating to toners with a crosslinking compound, reference for example column 4, lines 42 to 64.
However, there is a need for new toner resins that possess desirable characteristics, and that are useful in electrophotographic imaging systems. Additionally, there is a need for economical toner compositions wherein a highly crosslinked single styrene resin is selected enabling toners for incorporation into xerographic imaging apparatus where fixing can be accomplished without the utilization of release fluids, and the apparatus associated therewith. There is also a need for toner compositions which are useful in the development of images, and wherein fixing is accomplished without the need for release fluids. In addition, there is a need for resins useful for the formulation of toner compositions that possess desirable mechanical properties, stable electrical properties, excellent fusing characteristics, and acceptable release properties. Moreover, there is a need for developer compositions containing therein the toner components illustrated herein, and carrier particles. There is also a need for imaging and printing methods wherein there are selected toner and developer compositions containing therein the compositions illustrated herein, and wherein release fluids, such as silicone oils, are avoided during the fusing process. Moreover, there is a need for developer compositions containing therein a toner with specific crosslinked styrene resins, which toners possess relatively low fusing temperatures, 350.degree. F. for example, while maintaining high offset temperatures, 420.degree. F. or greater for example. Additionally, there remains a need for improved toner compositions that are compatible with fusing rolls incorporated into imaging apparatuses, especially Viton fuser rolls.